1. Field of the Invention
The present invention is directed to a method for prescribing control parameters for modulating the tube current (mA modulation) of an X-ray tube in a computed tomography system.
2. Description of the Prior Art
In the production of images of an examination subject by means of computed tomography, it is known that by automatic matching of the tube current to the patient attenuation, a good image quality can be insured while simultaneously optimizing the X-ray dosage. In order to calculate the correct tube current, the patient attenuation must be known.
Conventionally, current matching has been undertaken either on the basis of the expertise of the CT operator, or by evaluation of two orthogonal overview exposures (topograms). Examples of such conventional control procedures are described in U.S. Pat. Nos. 5,400,378 and 5,379,33 and 5,696,507. The necessity of producing two topograms results in exposure of the patient to an additional radiation dose. It would be desirable, therefore, to be able to achieve sufficient precise modulation of the tube current using only a single topogram.